Influence of different Zinc Coatings on the Electrode Wear and Resistance Spot Weldability of thin Sheet Steels (JOIN A10)

The weldability of steel components using the resistance spot welding process is of particular interest, especially in the automotive industry, since every car has approximately 5000 welds in its assembly process. Recently, there have been severe requirements by car industries to have more corrosion resistant coatings, which has increased the use of galvanized coatings on steel sheets to extend product life and improve product quality. The presence of zinc on the steel sheet surface, however, increases the electrode wear during welding and causes a decrease in electrode lifetime. In the case of hot dip galvanized steels, the electrode lives may be as low as 1500 spot welds, compared to the lives in excess of 10,000 welds for bare steels. In a high productivity process like resistance spot welding, the costs of replacing electrodes and the time associated with changing damaged electrodes can be very high. Also, the uncertainty in electrode life can lead to the production of defective welds in critical automotive components. It is therefore important to understand the relationship between welding and process variables and electrode degradation in order to optimize the production in terms of weld quality and cost.